noonday vs noontime

noonday

noun
  • The time of noon; the time of day when the sun is highest in the sky, especially on a hot day. 

  • The time of greatest prosperity. 

noontime

noun
  • Approximately noon. 

  • Noon. 

  • The time at which something peaks in some way (e.g., in vitality, in influence, in reknown) (by analogy with the waxing of the sun each day). 

How often have the words noonday and noontime occurred in a corpus of books? (source: Google Ngram Viewer )